Various electron tubes have been proposed. The electron tubes have a photocathode that emits photoelectrons in response to an incident light and a detection section constituted by a semiconductor device or a multiple-stage dynode that amplifies the photoelectrons so as to detect them.
As an electron tube using the multiple-stage dynode, there is available an electron tube in which a photoelectron emission photocathode is formed on a faceplate provided at the end portion of a tubular envelope and a multiple-stage dynode is provided opposed to the faceplate. This electron tube has, on the faceplate, an evaporator for depositing a material for use in formation of the photoelectron emission cathode. The evaporator is provided outside a tube surrounding the dynodes and prevents the material evaporated from the evaporator from being adhered to the dynodes. Further, a plurality of focusing electrodes is provided in the electron tube. These electrodes prevent the material evaporated from the evaporator from being adhered to an unintended portion, such as the internal wall of the envelope (refer to, for example, Patent Document 1).
As an electron tube using the semiconductor device, there is available an electron tube that encapsulates therein an electron-irradiated type diode. In this electron tube, a shied plate that restricts the electron path is provided around the semiconductor device (refer to, for example, Patent Document 2).
As an electron tube using an avalanche photodiode (hereinafter, referred to as APD) as the semiconductor device, there has been proposed an electron tube in which an entrance window and a conductive stem are disposed opposite to each other at both ends of an insulating container; a photocathode is formed on the internal wall of the entrance window; and the APD is disposed on the conductive stem. The conductive stem protrudes in the direction toward the photocathode. In forming the photocathode on the entrance window, metal vapor such as alkali metal vapor are injected through a through-hole formed in the insulating container, in a predetermined order to allow the metal vapor to react with previously deposited antimony (refer to Patent Document 3).
[Patent Document 1]
Japanese Patent Application Laid-Open Publication No. 2-288145 (pages 3 to 4)
[Patent Document 2]
Japanese Patent Application Laid-Open Publication No. 6-318447 (pages 5 to 8, FIG. 1)
[Patent Document 3]
Japanese Patent Application Laid-Open Publication No. 9-297055 (pages 4 to 9, FIG. 4)